Assessment of six different methods for the estimation of surface ultra-violet components at one location in Uruguay

Abstract

This communication assesses six methods estimating Ultra-Violet A and B (UV-A and UV-B) fluxes from satellite imagery, numerical weather modelsorground measurements. The UV estimates from each method are compared to coincident 15 minutes in-situ measurements collected at one location in Uruguay from September 2015 to January 2019. The first method combines Global Horizontal Irradiance (G) measured on site with satellite-derived daily Ozone concentration. The second method uses an empirical model onto satellite-retrieved solar broadband irradiance at the surface (SSI) produced by HelioClim-3version 5 (HC3v5) to derive UV fluxes. The third method named CAMS-UV, is one of the outputs of ECMWF numerical weather model. The three remaining methods rely on more sophisticated modellingof the atmosphere in cloud-free conditions using radiative transfer modellingcombined to a cloud modification factor (or cloud extinction) derived from HC3v5. Outside anunderestimation observed for the UV-B range for bothCAMS-UV (-20 %)andforthe empirical model (-29%),methods demonstrated their ability to collect the temporal variability of the signal of the instrument on-ground;biases ranges from-2to 4% for UV-A andfrom0 to 10 %for UV-B, RMSE are close to 15 %and almost all correlation coefficients exceed 0.96. This analysisgivesprecious elements for discussion about the performance of models mainly developed and validated over Europe and Africa.